<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
      div {
            width: 200px;
            height: 200px;
            background-color: yellow;
            margin: 10px;
        }
        #div2,#div3 {
            width: 100px;
            height: 100px;
            float: left;
            background-color: red;
        }
        #div4 {
            clear: both;
        }
    </style>
</head>
<body>
<div id = "div1">div1</div>
<div id = "div2">div2</div>
<div id = "div3">div3</div>
<div id = "div4">div4</div>

</body>
</html>